A study reported last year of factors influencing plasma glucose and insulin levels in the basal state and after an oral glucose challenge has been published. The Diabetes Prevention Program (for Type II diabetes) has been initiated; recruitment among the 25 Centers is under way. BLSA participants who meet the established inclusion/exclusion criteria will be referred to the Johns Hopkins Center or to a center close to their place of residence. This is the first example of referral of BLSA participants to an interventive study in its 38-year history. Both the American Diabetes Association and the World Health Organization have established committees to consider modification of guidelines for the diagnosis of diabetes that have been in place since 1979-80. The major underlying reason for dissatisfaction with current standards is the discrepancy between diagnostic standards established for the fasting (140 mg/dl) and the two-hour post-glucose (200 mg/dl) plasma glucose levels. The fasting outpoint detects a much smaller percentage of diabetics than does the two-hour outpoint. We have therefore examined the results of 5590 glucose tolerance tests obtained in the men and women of the BLSA population. The sensitivity, specificity, positive and negative predictive values, and ROC curves (Receiver Operating Characteristic) are being generated for men and women and the effect of age on these variables is being analyzed. This is a very large experience and should provide useful evidence in reaching decisions concerning new diagnostic standards for diabetes.